1. Field
This method and invention relates to recovering drilling tools and objects from wells. More particularly, it is a fishing tool apparatus and method for determining the orientation of an object before recovering said object by means of a flash weld.
2. State of the Art
In downhole drilling, long drill stems are used to drive drilling equipment and bits located at the bottom of the hole. The length of the stem generates extreme tensions and pressures on the drilling system, ocassionally causing severence or breakage. When pieces of the drilling equipment detach, they must be removed from the hole before further drilling. To remove these objects from the well, various fishing tool devices have been developed. W. W. Gipson, U.S. Pat. No. 2,218,131 discloses a device to recover objects by flash welding electrodes to the object and then retrieving the electrodes with the object attached. The device has a plurality of electrodes which are brought into contact with the object by cables, drill pipe, etc. and flash welded to said object. A. L. Armentrout et al, U.S. Pat. No. 2,154,654 is another fishing tool using welding electrodes. It includes an air source associated with the electrodes to provide an air screen to shield the electrodes for better welding contact between the object and the electrodes. It also includes means to indicate when the electrodes contact the object. Foster, U.S. Pat. No. 2,789,004 uses a plurality of thermite cartridges, instead of electrodes, for welding the fishing tool to the object. These cartridges are brought into contact with and welded to the object. Retrieval of the object is accomplished in a similar fashion as electrode fishing tool devices.
Because the objects to be retrieved may not be centrally aligned within the well bore, the electrodes, or thermite cartridges, may attach to the object in a position which causes the object to wedge against the bore as the fishing tool is withdrawn. Thus, there is a need to determine the orientation of the object in the well before welding an electrode or thermite cartridge to the object. Presently a lead impression block is used for this purpose. The lead block is lowered from the surface and brought into contact with the object. The lead block is then pounded against the object until an impression in the block of the object is formed. The lead block is then withdrawn and inspected to determine the orientation of the object. A fishing tool is then inserted to flash weld to and retrieve the object. This procedure requires the drill stem to be dissassembled and assembled twice to retrieve an object. Also, since the lead block may rotate upon withdrawal, the direction of the lie of the object cannot be precisely determined. Thus, a weld may be etfectuated with an electrode or thermite cartridge attaching at a point which causes wedging when the fishing tool is withdrawn.
C. F. Farmer, U.S. Pat. No. 3,441,307, discloses an electromagnetic well service tool which retrieves ferro-magnetic objects by use of strong electromagnets. These electromagnets are attached to the fishing tool and brought into contact with the object to be retrieved. The magnets are then activated to magnetically attract the object. The electromagnets, with the object attached, are then withdrawn from the well. These electromagnetic well service tools may lose objects if the electromagnetic field is weakened by conditions encountered within the well upon withdrawal. Also, the electromagnets carrying an object may attach to well casings upon withdrawal, dislodging the object.